Preheat oven to 400 degrees
Line a rimmed baking sheet with parchment paper and put carrots on it in a pile. Drizzle with olive oil and season with pepper and garlic salt
Toss around to coat carrots and spread into an even layer. Cook for 30 minutes or until carrots are soft when pierced. Reduce oven temperature to 375 degrees.
While carrots are roasting, saute mushrooms with butter and a drizzle of olive oil in a skillet on medium high, stirring only occasionally until mushrooms are golden on both sides. Set aside.
Snap tough ends off asparagus and rinse. Wrap in a clean towel and microwave on high for 2 minutes. Immediately unwrap asparagus to prevent further cooking and place on cutting board to cool
Put dough round on a piece of parchment paper and spread with a thin layer of prepared sauce, leaving a one inch border.
Cut asparagus into one inch pieces
Top sauce and dough round with a layer of carrots and sprinkle with cheese
Add mushrooms in an even layer and sprinkle with more cheese
Top with asparagus pieces and another sprinkle of cheese
Fold dough up and over the layered vegetables, folding dough into pleats as you go around the edge.
Transfer galette onto a baking sheet, holding the parchment paper on each side and carefully lifting and sliding on to sheet.
Bake at 375 degrees for 30-40 minutes or until dough is golden and cook through
Cut into large wedges for main dish or smaller wedges for a side dish